Distributed denial of service (DDoS) attacks are increasingly popular with cybercriminals, security researchers have revealed.
These services are making it easier to carry out DDoS attacks by offering thousands of hijacked computers for attacking websites to the highest bidder.
The researchers said these botnets are capable of knocking even some of the most-protected sites offline. To promote these botnets, cybercriminals will even offer a "demo" performance for a few minutes to prospective buyers, they said.
"In the last quarter, McAfee Labs observed many new denial-of-service attacks, including some that demand ransom," the report said.
Four Australian sports betting companies were taken down during key events like the national football and rugby league finals, resulting in millions of dollars of losses.
The McAfee report also found that spam and malware levels have reached an all-time high, with threats surpassing previous records in the last quarter.
Web-based attacks have also increased as cybercriminals take advantage of celebrity deaths and natural disasters.
Spam reached its highest level in history, breaking the previous record set in the second quarter of 2009 by 10%.
Spam now makes up 92% of all e-mail, jumping 24% compared with the same period a year ago.
Web-based attacks are the most popular means of attack, and have become one of the most dangerous tools cybercriminals use.
These attacks can target anyone who visits a malicious web page, the report said, and are delivered to users through spam, phishing, social networks and even through redirects from hijacked legitimate websites.
Cybercriminals are getting increasingly effective at utilizing search engine optimisation (SEO) techniques to drive traffic to these bad sites.